1. Field of the Invention
The present invention relates to a solid state image sensor device and a method of manufacturing the same, which are used for a CCD (charge coupled device) in particular.
2. Description of the Related Art
Conventionally, a photocell section of a CCD comprises, as shown in, for example, FIG. 10, an Si substrate 101, a gate insulating film 102, a first-layer electrode 103, an insulating interlayer 104, a second-layer electrode 105, a second insulating interlayer 106, a light shielding film (layer) 107, a planarized layer 108, and microlens 109. Incident light is condensed by the microlens 109 and received at a light-receiving portion.
In the manufacture of the CCD thus arranged, a material, such as a polysilicon, for a first-layer electrode is deposited on a gate insulating film 102. The first-layer electrode's material is patterned with a patterned resist, not shown, as a mask to provide a first-layer electrode 103 (see FIG. 11A).
The surface area of the first-layer electrode 103 is oxidized to provide an insulating film 104 of the order of 0.2 .mu.m. Thereafter, a second-layer electrode's material is deposited on a surface. The second-layer electrode's material is etched with the use of a patterned resist, not shown, as a mask to provide a second-layer electrode 105 (see FIG. 11B).
In the CCD structure above, the first-layer electrode 103 and second-layer electrode 105 are stacked in a cross-section taken along a line X--X. That is, in the conventional CCD structure, as shown in FIG. 10, the first-layer electrode 103 and second-layer electrode 105 are nearly fully superimposed as shown in FIG. 10 to minimize an electrode-to-electrode distance.
Since, however, a stacked structure of the first-layer and second-layer electrodes 103 and 105 has a greater step at its edge portion, the light shielding film 107 has to be adequately thickened so as to cover the side wall portions of the first-layer and second-layer electrode 103 and 105. The light shielding film 107, being not required at some part, is removed at a later step. In the case of the light shielding film 107 being thick, it will be difficult to fully remove the light shielding film 107. There is a disadvantage that part of the light shielding film 107 is left in particular at a great step in an etching process.
Further, if the light shielding film 107 is thickened, it shields part of an optical path of incident light condensed at the microlens 109, thus lowering the sensitivity of the device.
In the conventional device, as set out above, the greater step is provided at the edge portion of the stacked structure of the first-layer and second-layer electrodes 103 and 105. This necessitates thickening the light shielding film 107 and there arises the problem with the remaining of the light shielding film at the etching step and the consequent reduced sensitivity.